Field of the Disclosure
This disclosure generally relates to power supplies, and specifically to a feedback scheme for non-isolated power supplies.
Description of the Related Art
Switching power supplies are categorized into either isolated power supplies or non-isolated power supplies. In isolated power supplies, a transformer is placed between the input and output that provides galvanic isolation between the input and output. Non-isolated power supplies include a single inductor and do not have a galvanic isolation between the input and output. In a non-isolated power supply that operates on high voltages, a high voltage isolation device is typically needed to send the information about the output voltage to control the power switch. For example, a high voltage diode can be used to handle voltages as high as (or higher than to account for switching overshoots) 155V.
A conventional feedback scheme in a high voltage buck converter uses a high voltage diode (e.g., DFB in FIG. 6) or a high voltage bipolar junction transistor (e.g., T2 in FIG. 7)) to send the information about the high output voltage back to a controller that generates a control signal for controlling the power switch. One disadvantage of the conventional approach is the necessity of a high voltage diode (e.g., FIG. 6) or a high voltage BJT (e.g., FIG. 7) that is expensive. Another disadvantage is a limitation on the ability to sense the output voltage only once per switching cycle and only after the switching in that cycle that increases recovery from, for example, a standby mode.